Let-off mechanism for looms



June 3, 1930. H. H. BURDETT v LET-OFF MECHANISM FOR LOOMS Filed June ll, 1929 3 Sheets-Sheet 1 v //Vl E/\/TOR A T TOR/VEY June 3, 1930. BURDETT 1,761,611

LET-OFF MECHANISM FOR LOOMS Filed June 11, 1929 3 Sheets-Sheet 2 ATTORNEY June 3, 1930. H. H. BURDETT LET-OFFMECHANISM FOR LOOMS Filed June 11, 1929 3 Shee ts-Sheet 3 //VI/ENTOR" A TTORNEY Patented June 3,,

UNITED STATES PATENT OFFICE HORACE H. BURDETT, OF HOPEDALE, MASSACHUSETTS, ASSIGNOR '10 DRAPER CORPO- RATION, OF HOPEDALE, MASSACHUSETTS, A CORPORATION OF MAINE LET-OFF MECHANISM FOR LOOMS Application filed June 11,

This invention relates to let-ofi mechanisms for looms whereby the warp is sup plied in proper amount to the weaving instrumentalities.

Let-01f mechanisms for looms may now enerally be classed as of two types, one, l nown as the positive let-off, wherein the warp beam is positively rotated to supply the warp, and the other a friction let-off wherein the warp beam issubjected to means for exerting friction thereon. The present invention is more particularly directed to the positive type of let-off mechanism of the general character now known as the Roper letoff, as exemplified in the- Roper Patent, No.

7 44,941, dated November 24:, 1903.

In the so called Roper let-off the warp beam is provided with a gear meshing with a pinion fast on a driving shaft, on which latter a ratchet is loosely mounted,and motion is transmitted to the driving shaft through a train of speed reducing'gearing. The speed reducing gearing comprises an internally toothed gear secured to the driving shaft and meshing with a non-rotatable externally toothed gear of less number of teeth and loosely mounted on an eccentric connected to the ratchet, an arm being employed and connected with the externally toothed gear to prevent its rotation. By reason of the dif-- ference in the number of teeth on the two gears, the internally toothed gear willrotate slowly by reason of its engagement with the non-rotatable externally toothed gear as the latter travels within the internally toothed gear and in mesh therewith.

In the practical operation of the Roper let-01f it has been found that the warp beam slows down and then increases its speed at regular intervals entirely independent of the warp tension or the diameter of the yarn mass on the beam. This irregularity of letofl does not materially produce noticeable effects in a large number of fabrics, but in some of the finer grades objectionable streaks appear in the cloth.

One of the objects of the present invention is to so improve the positive let-ofi of the Roper type as to entirely eliminate the periodic'irregularity in let-ofi', and consists 1929. serialno. 370,066.

in means associated with the speed changing mechanism for producing an even and unvarylng rotative movement to the warp beam throughout the loom operation, thereby eliminating any objectionable streaks in the finer grades of fabrics.

The invention and novel features thereof will best be made clear from the following description and the accompanying drawings of one good form thereof.

In the drawings:

Fig. 1 is a side elevation of a loom having a positive let-off provided with the present invention;

Fig. 2 is a sectional rear elevation on an enlarged scale on the line 2-2 of 1;

Fig. 3 is an enlarged detached detail showing the relation of the internally and externally toothed gears and the gear holder;

Fig. 4 is a section on the line 44 of Fig. 3; Fig. 5 is an enlarged section on the line 55 of Fig. 2; r

Fig. 6 is a face viewof the cage containing anti-friction rollers to be interposed between the externally toothed gear and the eccentric on which it is loosely mounted; and

Fig. 7 is an edge elevation of Fig. 6.

The loom frame l may be of usual construction for proper support of the operating parts, and the lay 2- is supported by the lay swords 3 mounted for rocking movement on the lay rock shaft 4. The lay is given its beat-up movements through a pitman 5 connected to the crank shaft 6, as usual.

. The warp beam 7 is provided with a large gear 8 meshing with a pinion 9 secured to the driving shaft 10, and loosely mounted on the driving shaft is the ratchet 11 which is given its step-by-step-movement through a pawl 12 mounted on a pawl carrier 13 which may be conveniently supported upon the driving shaft 10. Extending downwardly from the pawl carrier 13 is an arm 14 connected to a rod 15 having a slotted end portion 16 embracing a stud 17 on a rocker arm 18 secured to the lay rock shaft. The amplitude of pawl movement is controlled throu h an arm 19 which bears upon the mass 0 warp on the warp beam and is pivotally mounted at 20. The arm 21 is connected to a radius arm 22 carrying a roller 23 having sliding engage ment with the pawl carrier 13'and the pawl setter 24 which is pivotally mounted at 25 (Fig. 1) and connected by a rod 26 to the rocker arm 27 extending from the rock shaft 28, from which project thewhip roll carrying arms 29. All of the above parts, including the spring 30 on the rod-26, which is itself connected to the pawl setter arm 24, are or may be of the same general character as more fully described in the Roper patent above mentioned.

Between the ratchet 11 and the driving shaft 10 is the speed reducing mechanism, comprising the eccentric 31 connected to the ratchet 11, and the externally toothed gear 32 loosely mounted on the eccentric and having teeth which mesh with the teeth of an internally toothed gear 33 secured to the driving shaft 10, and these parts as thus far described may bev of the same general character as similar parts in the Roper patent.

The internally toothed gear 33 may be secured to the driving shaft 10 by any suitable means, but as'herein shown the face of the internal gear is provided with a series of ratchet teeth 34 which are engaged by a detachable finger. 35 rising from the hub portion 36 of the finger carrier 37 which is secured to the driving shaft 10 by a bolt 38.

The externally toothed gear 32 which, as previously described, is loosely mounted upon the eccentric 31, is provided with pins. 39 on each of which is rotatably supported.

a roller 40. Each of the rollers 40 extends into a slot 41 of the projecting portions 42 of a ear iolder 43, one end of which is provide with a slot 44 embracing the shaft 20, whereby the gear holder may have sufficient longitudinal movement to accommodate the similar but nonrotative movement of the externally toothed gear 32 as it travels about the internally toothed gear 33, and by reason of its less number of teeth imparts slow rotative movement to the gear 33 which is secured to the driving shaft.

From the construction thus far described it will be apparent that the externally toothed gear 32 will be raised by the eccentric during part of the eccentric movement and subsequently loweredas the externally toothed gear partakes of its circular movement Within the internally toothed gear. As the externally toothed gear 32 is raised by the eccentric, the weight of the gear and of the projecting portion of the eccentric will cause a retardation to the let-off, and, conversely, when the externally toothed gear '32 moves in a downward direction in its circular path, the weight thereof and of the eccentric contribute to increasing the speed of let-off.

Under the construction thus far described it will be apparent that the unevenness of let-ofi' will be manifested periodically during one cycle of the circular movement of the externally toothed gear, and one of the purposes of the/present invention is to provide means for eliminating the unevenness of letoif thus indicated.

As one simple means to this end, the present invention contemplates the provision of a counterbalance associated with the eccentric to compensate for the variation in gravity effect of the eccentric and externally toothed gear during the circular movement of the latter.

To the above end, the present invention provides a weight 45 shown as secured to the ratchet 11 at a point opposed to the high part of the eccentric, with the result that as the eccentric turns and raises the externally toothed gear 32, the weight 45 will be disposed in a diametrically opposite position to the high part of the eccentric, to thereby compensate for the increased weight both of the eccentric and externally toothed gear as they travel upward in the circular path of movement of the gear, and as the eccentric turns to carry the externally toothed gear in a downward direction in its circular path, the weight 45 will act in opposition to the gravity effect of the eccentric and toothed gear.

The weight or counterbalance 45 may be conveniently associated with the eccentric by securing the weight to one of the radial arms 46 of the ratchet 11, as indicated in Figs. 2 and 5, and in order to vary the counterbalancing effect of the weight, it may be adjustably secured in position by means of a slot 47 (Fig. 2) through which is passed a securing bolt 48.

Thus, during the circular movement of the externally toothed gear within the internally toothed gear, all variable tendency for pcriodic, uneven let-off is eliminated.

As contributing to the evenness of let-off which is primarily furnished by the counterbalance as hereinbefore described, there is interposed between the externally toothed gear 32 and the eccentric 31 a series of antifriction bearings, consisting, in the present instance of the invention, of a cage 49 (Figs. 6 and containing a series of anti-friction rollers 50 which may be held within the cage by any suitable means, but as herein shown by a spring wire 51.

During the circular movement of the externally toothed gear 32 and its transmission of movement to the internally toothed gear 33, a slight twisting or binding effect may result between the gear holder and the externally toothed gear where the latter is provided with rigid engaging lugs, and such twisting or binding effect is eliminated in accordance with the present invention by the rotatable rolls 40 carried by the pins 39 extending from the face of the externally toothed gear 32.

As shown, the ratchet 11 may be provided with a brake 52 for steadying the ratchet movement, and such brake may be substantially the same as that in the Roper patent hereinbefore mentioned. What is claimed is:

1. In a let-oft mechanism for looms, the combination of the warp beam, a shaft connected to-the warp beam to positively rotate it to let-off the warp, a ratchet loosely mount-' counterbalance the eccentric and externally toothed gear in their movements that the letoff may be rendered uniform throughout the rotation of said shaft. 2. In a let-ofi' mechanism for looms, the

combination of the warp beam, a shaft having a ratchet loose thereon, transmitting connection between the shaft and warp beam to effectrotation of the latter, speed reduction gearing between the .ratchet and shaft to rotate the shaft and comprising an externally toothed gear mounted loosely and eccentricallyvon the ratchet, an internal gear in mesh with the externally toothed gear and fast to the shaft, a weight for counterbalancing the externally toothed gear as'it is raised and lowered by the eccentric that the let-off may be uniform through a complete circular movement of the externally'toothed gear, and means for holding the externally: toothed gear from rotation.

3. In alet-oif mechanism of the character described, the combination of the warp beam and means for rotating it to positively letofi' the warp, including speed reduction gearing comprising intermeshing external and internal gears, an eccentric on which the external gear is loosely mounted, an arm connectedto the external gear to hold it from turning, a weight connected to the eccentric to counterbalance the external gear as it travels within the internal gear that the let-off imparted to the warp beam by the internal gear may be uniform throughout the circular bodily movement of the external gear.

- 4. In a let-ofl mechanism of the character described, the combination of the warp beam and means for rotating it to positively let-off.

the warp, including an internally toothed gear, an externally toothed gear intermeshing therewith, a rotary eccentric on which the externally toothed gear is loosely mounted, anti-friction bearings between the eccentric and externally toothed gear, aweight connected to the eccentric to counterbalancethe externally toothed gear as. it travels within the internally toothed gear that the rotation imparted to the warp beam to let-off the warp may be uniform throughout the movement of the externally toothed geari 5. In a let-off mechanism of the character described, the combination of the warp beam and means for positively rotating it to let-ofi the warp, including an internally toothed gear and driving connections between it and the warp beam, an externally toothed gear intermeshing therewith, a rotary eccentric on which the externally toothed gear is loosely mounted, a counterbalance for theexternally toothed gear and eccentric and acting at the low side of the eccentric, a gear holding am having side projections provided with slots, pins extending from the face of the externally toothed gear, and anti-friction rolls mounted upon the pins for rotative movement and extending into the slots of the gear holding arm.

6. In a let-off mechanism of the character described, the combination of the warp beam and means for positively rotating it to let-off toothed gear acting at the low side of the eccentric, anti-friction bearings between the eccentric and the loosely mounted externally toothed gear, a gear holding arm having side projections provided with slots, pins extending from the face of theexternally toothed gear, and anti-friction rolls mounted upon the pins for rotative movement and extending into the slots of the gear holding arm.

7. In a let-off mechanism of the character 7 described, the combination of the warp beam and means for positively rotating it to let-off the warp, including an internally toothed gear and driving connections between, it and the warp beam, an externally toothed gear intermeshing therewith, a rotary eccentric on which the externally toothed gear is loosely mounted, a gear holding arm having side projections provided with slots, pins extending from the face of the externally toothed gear, anti-friction rolls mounted upon the pins for rotative movement and extending into the slots of the gear holding arm, and a weight connected to theeccentric and acting at the low side thereof to counterbalance the externally toothed gear as it travels within the internally toothed gear that the rotation imparted to the warp beam to let-off the warp may be uniform throughout the circularmovement of the externally toothed gear. 8. In a let-oft mechanism for looms, the

combination of the warp beam having an atgear to prevent rotation thereof, and a weight connected to the ratchet for counterbalancmg theexternally toothed gear as it travels within the internally toothed gear that the rotative movement of the warp beam to let-ofi' the warp may remain uniform during the complete circular movement toothed gear.

of the externally In testimony whereof, I have signed my name to this specification.

HORACE nniznnrr. 

